Air operated fastener driving tool, especially for tacks

ABSTRACT

A fastener driving tool in which tacks, connected at the head end thereof to form a flexible band, are fed seriatim by a reciprocating feed pawl from a magazine through a guide channel beneath a reciprocating driver which shears off the leading tack from the band and drives it into material located therebeneath. The feed pawl and the driver are reciprocated by air operated pistons in proper sequence and a pawl or tooth movable transverse to the direction of the flexible band and operatively connected to a sliding block on which the feed pawl is mounted is provided to prevent movement of the band during shearing off the leading tack therefrom.

United States Patent 1191 Inzoli et a1.

[ 1 Dec. 17, 1974 1 1 AIR OPERATED FASTENER DRIVING TOOL, ESPECIALLY FOR TACKS [76] Inventors: Giovanni Inzoli; Enrico Arosio; 7

Stefano larrera, all of Via Don Minzoni 21, Bresso, ltaly 22 Filed: 0 1. '4, 1972 21 Appl. No.1 294,865

[52] U.S. C1 227/136, 227/149, 227/130 [51] Int. Cl. B25C-1/04 [58] 'Field of Search 227/136, 149, 130

[56] References Cited UNITED STATES PATENTS 7 1,310,590 7/1919 Warnke 227/149 X 2,319,748 5/1943 Rhodes 227/149 2,373,509 4/1945 Speth 227/149 2,829,370 4/1958 Humbert 227/149 X 3,134,981 6/1964 Demetrakopoulas et al 227/149 3,398,446 8/1968 Karlsson 227/149 X 12/1970 Obergfell 227/136 3,572,572 3/1971 Readyhough 227/130 3,688,966 9/1972 Perkins et al. 227/136 3,708,097 1/1973 Fisher 227/136 Primary ExaminerGranville Y. Custer, Jr. Attorney, Agent, or FirmMichael S. Striker 5 7] ABSTRACT A fastener driving tool in which tacks, connect ed at the head end thereof to form a flexible band, are fed seriatim by a reciprocating feed pawl from a magazine through a guide channel beneath a reciprocating driver which shears off the leadingtack from the. band and drives it into material located therebeneath. The feed pawl and the driver are reciprocated by air operated pistons in proper sequence and a pawl or tooth movable transverse to the direction of the flexible band and operatively connected to a sliding block on which the feed pawl is mounted is provided to prevent movement of the band during shearing off the leading tack therefrom.

14 Claims, 29 Drawing Figures PATENTEE DEC] 7 I974 SHEET 10F 4 1 AIR OPERATED FASTENER DRIVING TOOL, ESPECIALLY FOR TACKS This invention relates to an air operated device, particularly for quick insertion of tacks and the like.

Isis well known that the quick automatic insertion of tacks and the like represents a problem, which has not yet been rationally solved, because of the difficulty of inserting the tacks, so that their shanks are aligned with the direction of driving. This is particularly difficult when the device has to be actuated in an inclined position as-often occurs in upholsterywork.

It isthe specific object of this invention to provide an air operated device which can successfully solve the problem, inasmuch as it ensures the sequential insertion of a plurality of tacks in a quick and rational manner even if used at different angular positions With this and other objects in view, which will become apparent as thedescription proceeds, the air operated fastener driving tool according to the present invention for driving tacks connected to each other at the head end to form a flexible band mainly comprises a cylinder, a piston arranged in the cylinder reciprocable between an active stroke toward one end of the cylinder and a return stroke, and a rod-shaped driver coaxially fixed at one end to the piston and projecting therefrom towards the one end of the cylinder. The tool includes further a magazine for receiving the tacks connectedto each other inthe form of a flexible band, a

guide channel extending between the magazine at theone end of the cylinder for guiding the band in longitudinal direction from the magazine to the one end of the cylinder, and feed means movable .between a feed stroke and a return stroke for placing at the end of the feed stroke the leading tack on the band in a position thereof adjacent to the one end of the cylinder to prevent the sheared off tack from returning into the feed channel and to prevent also further movement of the band during shearing off the leading tack therefrom.

The fastener driving tool preferably includes also yieldable guide means connected to the one end of the cylinder for guiding a tack driven by the driver.

These and further more specific characteristic features of the present invention will become more apparent from the following detailed description of a preferred, but non-limiting embodiment of the air operated device of this invention with relevant modified embodiments, when taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows the air operated device of this invention in a perspective view;

FIG. 2 is a detail of the normal positioning device of the tacks, viewed in an axial section with the striking piston raised;

FIG. 3 shows the samedevice as FIG. 2, but with piston lowered;

FIG. 4 represents the layout of the pneumatic circuit as used for the control of the feed piston and striking piston with the aid of a trigger;

FIG. 5 shows in a perspective view one of the sectors of the positioner and related spring-loaded means;

FIG. 6 is a detail of the plastic band acting as support means for the tacks in a plan view;

FIG. 7 shows the same in a profile view with the tacks applied thereto;

FIG. 8 is a perspective view of the band with the tacks, wound in a spiral-like manner, ready to be located in the magazine,

FIG. 9 is a cross section of the guide duct of the band at the open section;

FIG. 10 is a cross section of the above guide duct at the end section;

FIG. 11 is a perspective view of the magazine of the band with the plate acting as loader;

FIG. 12 is a perspective view of the end portion of the guide duct of the band with the tack feed member in forward position;

FIG. 13 is a view similar to FIG. 12, but with the tack feed member in retracted position;

FIG. 14 is an axial section of the balance performing the closing of the tack guiding duct at the head;

FIG. 15 is a side view of a portion of the band with the tacks engaged in the feed tooth;

FIG. 16 is a side view of a modified embodiment of the positioner using tacks of reduced dimensions;

FIG. 17 is a top view of FIG. 16;

FIG. 18 is an axial section of the aforesaid positioner as fitted to the operating spindle and in rest condition;

FIG. 19 is a view similar to FIG. 18 and showing the elements under working conditions; 7

FIG. 20 is a perspective view of a further modification of the positioner in for a device using tacks of considerable diameter ,with an unclogging device applied thereto; I

FIG. 21 is a perspective view of two articulated jaws, dissociated from each other;

FIG. 22 is a perspective view of the closing means of the tack supply duct;

FIG. 23 shows the components, constituting it, dissociated from each other in a perspective view;

- FIG. 24 is a perspective view of the tack feed band formed with a guide member and balancing means by direct moulding of suitable plastic material and used for the insertion of metal tacks;

FIG. 25 is a plan view of the end section of said band with the balancing means;

FIG. 26 is a side view of FIG. 25;

FIG. 27 is a perspective view of a detail of the end portion of the band with the balancing means;

FIG. 28 is a perspective view of the feed band with the guide and balancing means, all being built as a unit by direct moulding of suitable plastic material; and

FIG. 29 is a perspective view of a detail of said band.

Referring now particularly to the figures in the accompanying drawings, the air operated device of this invention includes an elongated body provided with a handle 31 at one end of which there is located a magazine 32, closed by an articulated cover 33. An inlet 34 for compressed air is provided at one end of the handle. At the other end the handle 31 and the body are connected to a cylinder 35 normal thereto, containing a piston 36 from the lower end of which a driver 37 in form of a rod projects integral therewith. At the head of the cylinder 35 there is fitted a distributing valve 38 which, controlled by the trigger 40 feeds compressed air from a chamber 39 in the handle to the piston 36 and a second piston 41, actuating the feed means of the plastic material band 42 on which a plurality of tacks 43, 43, 43".

. are mounted. The band, which is provided on its front portion with a laterally extending handgrip 44, adapted to enable the operator to bring it intoa utilization position and which is then torn off, is wound in a spiral-like manner, FIG. 8, and is delivered, supported onto a plate 45, acting as loader into the magazine 32, with a control tube 47 on the plate; located for rotation on the central pivot 46 of the magazine, while its front portion enters the guide passageway 48, which connects the magazine to the operating head 49, placed axially under the cylinder 35 in which the driver 37 slides. At the lower end of the head 49, fitted with suitable collar, there are hooked up for swinging about tips 50 three similar cylindrical sectors 51 tapering toward the lower end, forming a tack guide and which are maintained radially associated with each other via a springloaded means 52 which is received in corresponding perimetral channels 53, formed on the cylindrical portion. Axially of the sectors, FIGS. 2 and 3, slides the driver 37, at the end of which there is formed a cavity 54, which fits the head of the tack on which it is designed to strike. While the initial portion of the guide duct 48 is laterally open, FIG. 9, in order to ensure the positioning of the band with the tacks, the end portion thereof, on which there is laterally applied a ball 55,

'maintained in thrust condition by a spring-loaded means 56, which is adjustable by means of a set screw 57, FIG. 10,'is laterally closed at its end portion extending into the operating head 49. The end of the duct 48 may be closed and opened by a tongue 58, articulated sideways by means of the angled lever 59 on which acts a lateral tooth 61 of a sliding block 60. It is to be understood that the sliding block 60 is guided on the body 30 by two oppositely arranged lateral teeth 61, and it is the rear tooth 61, not visible in FIGS. 12 and 13, which acts on the lever 59. The sliding block is connected to the shaft of the piston 41, which provides for its sliding with the aid of the spring-loaded means 62 placed therebetween. On the head of the block 60 there is articulated a pawl tilted forwardly and maintained under pressure on the band 42 and related tacks by the spring-loaded means 64, whereby, during the feed phase, because it is pushed by the spring-loaded means 64, it engages between one and the following tack, exerting a forward push, while in the return phase operated by the piston 41 it travels over the head of the following tack, engaging behind it, ready to perform another feed motion.

When the air operated device of this invention is to be used for large-scale industrial production there is provided a particular version of the tack positioner which includes, applied to the operating head 49, a hollow body 65 in the wall of which there is formed a window 66, which is shaped and dimensioned in relation to the tack type to be used such that the tack may reach a coaxial position with the driver 37. Opposite of the windows 66 there is provided an opening 67 through which it is possible to remove a tack in case of stopping, FIG. 20. On the lower portion of the body 65 there is provided a cylindrical portion 68 on which there are articulated facing each other two jaws 69, 70 maintained against each other by the respective elastic tongues 71 and 72 which permit them to spread the tongues apart when a tack is being pushed by the driver 74, is formed with a linear groove 79, inclined at an acute angle relative to the longitudinal direction of the guide channel, in which a member 80 is slidably arranged, projecting with its tooth-shaped end 82 beyond the block 78. A pin 81 projecting upwardly from the member 80 is received in a slot 76 formed in the lower arm of the U-shaped block 74 so that at the end of the feed stroke of the sliding block 60, the tooth-shaped end 82 of the member 80 will be located between the tack positioned beneath the driver and the nextfollowing tack, to avoid retraction of the positioned tack in the subsequent push phase. When the tack driving device is used for tacks of small diameter, particularly for craftsman use and light work, such as cardboard work and the like, a modified positioner is used which includes a conical hollow slotted body 83 of thin elastic material forming a plurality of convergent segments, e.g. 84, 84, 84" and 84", between which there is formed an axial hole for the passage of the stem of the tack, FIGS. 16 and 17. The body 33 is fitted to the operating head 49 with the aid of a correspondingly shaped ring 85 which, screwed onto the lower end of the head, presses the upper part of the body 23 against the head, leaving on the lower part a perimetrical space permitting the elastic expansion of the segments in radial direction when the head of a tack B passes therethrough at the time the driver 37 engages thereupon, FIGS. 18 and 19.

The band 86 for mounting the tacks is shaped like a spiral and formed of a plurality of circular portions, each provided with central hole into which there are inserted the metal tacks B of small diameter, FIG. 24, and connected to each other in succession by thin filaments. A grip portion 87, integral with the band, projects laterally from the region of the front end of the band for insertion of the latter into the tack driving device, whereas its end portion is provided with an integral balancing member 88, consistingvof a preferably trapezoid-shaped block, FIG. 27, and having a stem 89 similar to that of thetacks to maintain the last tack of the band properly positioned, thereby avoiding that by its overturning it might clog the positioner present in the device. When the tacks are being used for upholstery work, requiring their insertion into relatively yielding materials, such as masonite, cork, soft wood, cardboard panels, etc., the tacks made may be molded from plastic material together with the band with which they form one single'body: as a matter of fact, the tacks B are moulded together with the band taking on a spiral-like shape, FIGS. 28 and 29, at which the tacks are connected to each other in succession via short filaments, and similarly to the other bands, this, too, includes a laterally extending grip portion 87 and the balancing member 88. Such tacks, permitting considerable savings relative to metal tacks, may be made in different colours in accordance with market demands, adapting them to the application, which is not possible with metal tacks of current type, the colouring of which in a very limited colour range may only take place by painting or covering, which ultimately considerable increases their cost. The plastic tacks permit also a cleaning with detergents without altering the colours and a large-scale mass-production at low cost with simple equipment. 1

The operation of the air operated device of this invention is as follows: once the loader. 45 has been inserted with the tacks applied on the band into the magazine 32, the front portion of the band is inserted into the channel 48 by using the grip portion 87, which is then torn off, so that the head of one track is inserted forwardly of the feed pawl 63; the device is thus ready for use. By actuating the trigger 40 and bringing the operating head 49 at the point whereat it is desired to insert the front tack is pushed by the pawl 63 beneath the driver-37; and the latter subsequently actuated by the piston 36, strikes strongly the head of the tack, provoking at first the detachment from the rest of the band and subsequently the descent along the conical passage formed by the sectors 51, whereby it positions coaxial to the driver by means of which it is subsequently inserted at the selected point of the plane P to which it should be fitted. In order to avoid that the tack in its push phase might return with its stem to the guide passageway, the latter is closed at the front end by the tongue 58, actuated by the angled lever 59, engages at one end by the tooth 61 integral with the sliding block 60 on which there is articulated the feed pawl 63. Upon completion of the insertion, the piston 36 moves again upwardly, while the piston 41 drives back the block 60, provoking the displacement of the tongue 58, which opens the front end of the duct 48, and the displacement of the pawl 63 which moves behind the next tack, ready to cause the feed by a subsequent operation. The accurate positioning of the tacks during the feed motion is laterally controlled by the ball 55. When the driver 37 passes through the sector 51 the latter will be spread against the force of the spring-loaded means 52. Beneath the head of the tack remains obviously the corresponding section of the band, providing an advantage because besides protecting the laminate, on which it is applied, also permits a more elastic tightness.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of fastener driving tools differing from the types described above.

While the invention has been illustrated and described as embodied in a driving too] for tacks, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the pres-- ent invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can,-

by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning I and range of equivalence of the following claims.

What we claim is: l. A fastener driving tool, for driving tacks connected to each other at the head end to form a flexible band, comprising cylinder means having opposite ends; apiston arranged in said cylinder means reciprocable between an active stroke toward one end of said cylinder means and a return stroke; a rod-shaped driver coaxially fixed at one end to said piston and projecting therefrom toward said one end of said cylinder means; a magazine for receiving the tacks connected to each other in the form of a flexible band; guide channel means extending between and connected to said magazine and said one end of said cylinder means for guiding the band in longitudinal direction from said magazine to said one end of said cylinder-means; feed means movable between a feed stroke and a return stroke for placing at the end of the feed stroke the leading tack on the band in a position coaxial with the other end of said driver; actuating means for first actuating said feed means on its feed stroke and then said piston on its active stroke so that the driver will shear off the leading tack from the band and drive the tack into material adjacent said one end of said cylinder means; and means directly engaged by and cooperating with said feed means for closing part of said guide channel means at the end thereof adjacent said one end of said cylinder means to prevent the sheared off tack from returning into the feed channel means and to prevent also further movement of the band during shearing off the leading tack therefrom.

2. A tool as-defined in claim 1 wherein said guide channel means has a guide channel of substantially T- shaped cross section having a narrow central portion for guiding the stems of said tacks, said closing means closing only said central portion of said guide channel.

3. A tool as defined in claim 1, wherein said feeding means comprises a block arranged on said guide channel means for reciprocation between said feed stroke and said return stroke, a pawl pivoted on said block, spring means for biasing said pawl into engagement with said band, and cylinder and piston means connected to said block and actuated by said actuating means for reciprocating said block.

4. A tool as defined in claim 1, wherein said means for closing said guide channel means comprises a tongue, an angled lever integral with said tongue and pivoted on said guide channel means, and means on said feeding means cooperating with said lever for pivoting the same in a first direction during the feed stroke of said feed means for placing the tongue in front of said end of said guide channel means and for pivoting said lever in the opposite direction during the return stroke of said feed means.

5. A fastener driving tool for driving tacks connected to each other at the head end to form a flexible band, comprising cylinder means having opposite ends; a piston arranged in said cylinder means reciprocable between an active stroke and a return stroke; a rodshaped driver coaxially fixed at one end to said piston and projecting therefrom toward said one end of said piston means; a magazine for receiving the tacks connected to each other in the form of a flexible band; guide channel means extending between and connected to said magazine at said one end of said cylinder means for guiding the band in longitudinal direction from said magazine to said one end of said cylinder means, said guide channel means being provided in the region of said one end of said cylinder means with a window extending from the outer surface of said guide channel means to a guide channel extending longitudinally therethrough; feeding means movable between a feed stroke and a return stroke for placing at the end of said feed stroke the leading tack on the band in a position coaxial with the other end of said driver, said feeding means comprising a block arranged on said guide channel means for reciprocation between said feed stroke and said return stroke, a pawl provided on said block, spring means for biasing said pawl into engagement with the band, and cylinder and piston means connected to said block; actuating means for first actuating said cylinder and piston means for moving said feeding means on its feed stroke and then said piston on its active stroke so that the driver will shear off the leading tack from the band and drive the tack into material adjacent said one end of said cylinder means; and means cooperating with said feeding means for closing part of said guide channel means at the end thereof adjacent said one end of said cylinder means to prevent the sheared off tack from returning into said feed channel means and to prevent also further movement of the hand during shearing off the leading tack therefrom, said last-mentioned means comprising a U-shaped member fixed to said block and extending with an arm formed with a slot through said window, a member fixed to said guide channel means and formed with a groove arranged at an angle to said guide channel, and a movable member guided in said groove and having a pin extending into said slot of said arm of said U-shaped member.

6. A tool as defined in claim 1, and including yieldable guide means connected to said one end of said cylinder for guiding a tack driven by said driver.

7. A tool as defined in claim 6, wherein said yieldable guide means comprises three sectors tapering in a direction away from said one end of said cylinder means, cooperating pivot means on said one end of said cylinder means and adjacent ends of said sectors and mounting the latter for pivoting movement about axes substantially normal to the longitudinal direction of said driver and removable from said one end, annular means removably connected to said one end of said cylinder means and at least partly surrounding said sectors radially spaced therefrom for preventing accidental removal of said sectors from saidone end of said cylinder means, and yieldable biasing means biasing said sectors into circumferential engagement with each other.

8. A tool as defined in claim 7, wherein said sectors are provided at their outer surfaces thereof with circuniferential grooves, and wherein said yieldable biasing means comprises a ring of elastomeric material located in said grooves. I

9. A tool as defined in claim 6, wherein said yieldable guide means comprises two sectors tapering in a direction away from said one end of said cylinder means, said sectors being mounted on said one end of said cylinder means for pivotal movement about axes extending substantially normal to the longitudinal direction of said driver between a closed position at which flat faces thereof abut against each other and an open position, each of said sectors being provided with a cavity extending from said flat face thereof into'said sector and longitudinally through the same; and a pair of elastic strips fixed to said one end of said cylinder means and respectively engaging said sectors for biasing the latter to said closed position.

10. A tool as defined in claim 6, wherein said yieldable guide rneans comprises a hollow substantially conical member of thin elastic material engaging with its large diameter end said one end of said cylinder means and being formed at the other end with an opening and a plurality of circumferentially spaced slits extending from said opening toward said large diameter end, and an annular member releasably connected to said one end of said cylinder means and engaging said conical member in the region of its large diameter end for holding said conical member onto said one end of said cylinder means while being radially outwardly spaced from the slitted portion of the conical member to permit radial expansion of the latter.

11. A tool as defined in claim 1, wherein said magazine is substantially cylindrical and having a bottom wall and a central pivot pin projecting from said bottom wall into the interior of said magazine, and including a substantially circular loading plate adapted to receive thereon said band wound in a spiral, said loading plate having central pivot means adapted to be mounted on said pivot pin so that the loading plate with the spirally wound band thereon may be rotated about said pivot pm. 12. A tool as defined in claim 1, wherein said band is provided in the region of one end thereof with a laterally extending tearable grip portion and at the other end thereof with a balancing member.

13. A tool as defined in claim 1, wherein said flexible band is formed by tacks of plastic material integrally connected at the head end thereof by thin connecting portions of the same material.

14. A tool as defined in claim 1, and including an elongated handle extending substantially parallel to and spaced from said guide channel means and being connected at one end to said magazine andat the other end to said cylinder means, said handle being formed in the interior thereof with a reservoir for compressed air and having air inlet means communicating with said reservoir, said feed means comprising cylinder and piston means, and said actuating means comprising a trigger mounted on said handle and valve means on the other end of said cylinder means for supplying compressed'air in proper sequenceto the interior of said cylinder means and to the interior of the cylinder of said feed means. 

1. A fastener driving tool, for driving tacks connected to each other at the head end to form a flexible band, comprising cylinder means having opposite ends; a piston arranged in said cylinder means reciprocable between an active stroke toward one end of said cylinder means and a return stroke; a rod-shaped driver coaxially fixed at one end to said piston and projecting therefrom toward said one end of said cylinder means; a magazine for receiving the tacks connected to each other in the form of a flexible band; guide channel means extending between and connected to said magazine and said one end of said cylinder means for guiding the band in longitudinal direction from said magazine to said one end of said cylinder means; feed means movable between a feed stroke and a return stroke for placing at the end of the feed stroke the leading tack on the band in a position coaxial with the other end of said driver; actuating means for first actuating said feed means on its feed stroke and then said piston on its active stroke so that the driver will shear off the leading tack from the band and drive the tack into material adjacent said one end of said cylinder means; and means directly engaged by and cooperating with said feed means for closing part of said guide channel means at the end thereof adjacent said one end of said cylinder means to prevent the sheAred off tack from returning into the feed channel means and to prevent also further movement of the band during shearing off the leading tack therefrom.
 2. A tool as defined in claim 1, wherein said guide channel means has a guide channel of substantially T-shaped cross section having a narrow central portion for guiding the stems of said tacks, said closing means closing only said central portion of said guide channel.
 3. A tool as defined in claim 1, wherein said feeding means comprises a block arranged on said guide channel means for reciprocation between said feed stroke and said return stroke, a pawl pivoted on said block, spring means for biasing said pawl into engagement with said band, and cylinder and piston means connected to said block and actuated by said actuating means for reciprocating said block.
 4. A tool as defined in claim 1, wherein said means for closing said guide channel means comprises a tongue, an angled lever integral with said tongue and pivoted on said guide channel means, and means on said feeding means cooperating with said lever for pivoting the same in a first direction during the feed stroke of said feed means for placing the tongue in front of said end of said guide channel means and for pivoting said lever in the opposite direction during the return stroke of said feed means.
 5. A fastener driving tool for driving tacks connected to each other at the head end to form a flexible band, comprising cylinder means having opposite ends; a piston arranged in said cylinder means reciprocable between an active stroke and a return stroke; a rod-shaped driver coaxially fixed at one end to said piston and projecting therefrom toward said one end of said piston means; a magazine for receiving the tacks connected to each other in the form of a flexible band; guide channel means extending between and connected to said magazine at said one end of said cylinder means for guiding the band in longitudinal direction from said magazine to said one end of said cylinder means, said guide channel means being provided in the region of said one end of said cylinder means with a window extending from the outer surface of said guide channel means to a guide channel extending longitudinally therethrough; feeding means movable between a feed stroke and a return stroke for placing at the end of said feed stroke the leading tack on the band in a position coaxial with the other end of said driver, said feeding means comprising a block arranged on said guide channel means for reciprocation between said feed stroke and said return stroke, a pawl provided on said block, spring means for biasing said pawl into engagement with the band, and cylinder and piston means connected to said block; actuating means for first actuating said cylinder and piston means for moving said feeding means on its feed stroke and then said piston on its active stroke so that the driver will shear off the leading tack from the band and drive the tack into material adjacent said one end of said cylinder means; and means cooperating with said feeding means for closing part of said guide channel means at the end thereof adjacent said one end of said cylinder means to prevent the sheared off tack from returning into said feed channel means and to prevent also further movement of the band during shearing off the leading tack therefrom, said last-mentioned means comprising a U-shaped member fixed to said block and extending with an arm formed with a slot through said window, a member fixed to said guide channel means and formed with a groove arranged at an angle to said guide channel, and a movable member guided in said groove and having a pin extending into said slot of said arm of said U-shaped member.
 6. A tool as defined in claim 1, and including yieldable guide means connected to said one end of said cylinder for guiding a tack driven by said driver.
 7. A tool as defined in claim 6, wherein said yieldable guide means comprises three sectors tapering in a directioN away from said one end of said cylinder means, cooperating pivot means on said one end of said cylinder means and adjacent ends of said sectors and mounting the latter for pivoting movement about axes substantially normal to the longitudinal direction of said driver and removable from said one end, annular means removably connected to said one end of said cylinder means and at least partly surrounding said sectors radially spaced therefrom for preventing accidental removal of said sectors from said one end of said cylinder means, and yieldable biasing means biasing said sectors into circumferential engagement with each other.
 8. A tool as defined in claim 7, wherein said sectors are provided at their outer surfaces thereof with circumferential grooves, and wherein said yieldable biasing means comprises a ring of elastomeric material located in said grooves.
 9. A tool as defined in claim 6, wherein said yieldable guide means comprises two sectors tapering in a direction away from said one end of said cylinder means, said sectors being mounted on said one end of said cylinder means for pivotal movement about axes extending substantially normal to the longitudinal direction of said driver between a closed position at which flat faces thereof abut against each other and an open position, each of said sectors being provided with a cavity extending from said flat face thereof into said sector and longitudinally through the same; and a pair of elastic strips fixed to said one end of said cylinder means and respectively engaging said sectors for biasing the latter to said closed position.
 10. A tool as defined in claim 6, wherein said yieldable guide means comprises a hollow substantially conical member of thin elastic material engaging with its large diameter end said one end of said cylinder means and being formed at the other end with an opening and a plurality of circumferentially spaced slits extending from said opening toward said large diameter end, and an annular member releasably connected to said one end of said cylinder means and engaging said conical member in the region of its large diameter end for holding said conical member onto said one end of said cylinder means while being radially outwardly spaced from the slitted portion of the conical member to permit radial expansion of the latter.
 11. A tool as defined in claim 1, wherein said magazine is substantially cylindrical and having a bottom wall and a central pivot pin projecting from said bottom wall into the interior of said magazine, and including a substantially circular loading plate adapted to receive thereon said band wound in a spiral, said loading plate having central pivot means adapted to be mounted on said pivot pin so that the loading plate with the spirally wound band thereon may be rotated about said pivot pin.
 12. A tool as defined in claim 1, wherein said band is provided in the region of one end thereof with a laterally extending tearable grip portion and at the other end thereof with a balancing member.
 13. A tool as defined in claim 1, wherein said flexible band is formed by tacks of plastic material integrally connected at the head end thereof by thin connecting portions of the same material.
 14. A tool as defined in claim 1, and including an elongated handle extending substantially parallel to and spaced from said guide channel means and being connected at one end to said magazine and at the other end to said cylinder means, said handle being formed in the interior thereof with a reservoir for compressed air and having air inlet means communicating with said reservoir, said feed means comprising cylinder and piston means, and said actuating means comprising a trigger mounted on said handle and valve means on the other end of said cylinder means for supplying compressed air in proper sequence to the interior of said cylinder means and to the interior of the cylinder of said feed means. 